Composite overhead cable structure having high seal properties and a process for producing the same

Abstract

Disclosed is a composite overhead cable structure having high seal properties, comprising a metallic pipe, at least one layer of stranded metallic elongated conductor surrounding the outer periphery of the pipe, and an optical fiber cable disposed within and extending throughout the length of the pipe, wherein the metallic pipe comprises at least two metallic pipe sections which are arranged in alignment and connected at their respective confronting terminals having contours complementary to each other and wherein the metallic pipe has a specific structure of connection between the mutually adjacent pipe sections, such that a longitudinal through-weld extends along the entire length of the metallic pipe and such that a connecting turning weld extends between first and second different points on the longitudinal through-weld of the metallic pipe so as to turn around the axis of said metallic pipe, the first and second points being positioned at a distance which satisfies a specific relationship. The welded metallic pipe has no weld defects in the longitudinal through-weld thereof so that the metallic pipe has excellent seal properties and therefore, the composite overhead cable structure of the present invention is free from the danger that rain water or the like enters the pipe and adversely affects the optical fiber cable.

What is claimed is: 
     
       1. A composite overhead cable structure for electric and optical transmission, comprising: a metallic pipe having a substantially circular cross-section taken along a line perpendicular to the axis of said pipe,   at least one layer of stranded metallic elongated conductor surrounding the outer periphery of said metallic pipe in close contact with said outer periphery, and   an optical fiber cable disposed within and extending throughout the length of said metallic pipe,   said metallic pipe comprising at least two metallic pipe sections each having in its wall a longitudinal weld extending in a lengthwise direction of the pipe section, said at least two metallic pipe sections being arranged in alignment so that the longitudinal welds thereof are aligned,   the pipe sections which are disposed in adjacent relationship being connected at their respective confronting terminals having contours complementary to each other, wherein each confronting terminal comprises a complementary, terminal longitudinal portion extending, in a lengthwise direction of the pipe section, from the terminal point of said longitudinal weld of the pipe section on the side of said confronting terminal and a complementary, terminal turning portion extending between both ends of said complementary, terminal longitudinal portion of said confronting terminal so as to turn around the axis of the pipe section, so that a longitudinal through-weld extends along the entire length of said metallic pipe, said longitudinal through-weld being constituted of said longitudinal welds of the pipe sections and a connecting longitudinal weld formed by the welding of said complementary, terminal longitudinal portions of the pipe sections, and so that a connecting turning weld formed by the welding of said complementary, terminal turning portions of the pipe sections extends between first and second different points on the longitudinal through-weld of said metallic pipe so as to turn around the axis of said metallic pipe along a peripheral wall of said metallic pipe,   said first and second points being positioned at a distance which satisfies the following relationship: ##EQU6## wherein a' represents the length of the circumference of the substantially circular cross-section of said metallic pipe and b' represents the distance between said first and second points on the longitudinal through-weld of said metallic pipe.   
     
     
       2. A composite overhead cable structure according to claim 1, wherein said connecting turning weld extends helically around the axis of the metallic pipe. 
     
     
       3. A process for producing a composite overhead cable structure, comprising the steps of: (1) providing at least two metallic tapes having predetermined widths substantially identical to each other, each tape having a predetermined length and having opposite, first and second longitudinal side edges extending in parallel along the entire length of said tapes,   at least one terminal of each of said at least two metallic tapes having a contour such that when the tapes are arranged in alignment, the contours of the respective confronting terminals of said tapes are complementary to each other, wherein each contour assumes a straight or curved line extending across said tape between a first point on said first side edge and a second point on said second side edge, said first and second points satisfy the following relationship: ##EQU7##  wherein a represents the width of the tape and b represents the distance between said second point and a third point which is defined as an intersecting point of said second side edge of the tape and a straight line drawn across the tape from said first point in a direction vertical to said second side edge of the tape,   (2) arranging said at least two metallic tapes so that one metallic tape abuts against the adjacent metallic tape at their respective confronting terminals having contours complementary to each other,   (3) welding said metallic tapes at their abutting terminals to form a welded, extended tape,   (4) bending said extended tape into a substantially cylindrical shape so that said first side edge of the extended tape meets said second side edge of the extended tape to form a substantially cylindrical preliminary pipe, while inserting an optical fiber cable into the substantially cylindrical preliminary pipe being formed,   (5) welding together said first and second side edges of said substantially cylindrical preliminary pipe to obtain a welded metallic pipe having the optical fiber cable disposed within and extending throughout the length of said welded metallic pipe, and   (6) stranding a metallic elongated conductor around said welded metallic pipe.   
     
     
       4. A process according to claim 3, wherein said contour of the confronting terminals of the metallic tape assumes a straight line. 
     
     
       5. An optical fiber cable-containing metallic pipe for use in optical transmission, comprising: a metallic pipe having a substantially circular cross-section taken along a line perpendicular to the axis of said pipe, and   an optical fiber cable disposed within and extending throughout the length of said metallic pipe,   said metallic pipe comprising at least two metallic pipe sections each having in its wall a longitudinal weld extending in a lengthwise direction of the pipe section, said at least two metallic pipe sections being arranged in alignment so that the longitudinal welds thereof are aligned,   the pipe sections which are disposed in adjacent relationship being connected at their respective confronting terminals having contours complementary to each other, wherein each confronting terminal comprises a complementary, terminal longitudinal portion extending, in a lengthwise direction of the pipe section, from the terminal point of said longitudinal weld of the pipe section on the side of said confronting terminal and a complementary, terminal turning portion extending between both ends of said complementary, terminal longitudinal portion of said confronting terminal so as to turn around the axis of the pipe section, so that a longitudinal through-weld extends along the entire length of said metallic pipe, said longitudinal through-weld being constituted of said longitudinal welds of the pipe sections and a connecting longitudinal weld formed by the welding of said complementary, terminal longitudinal portions of the pipe sections, and so that a connecting turning weld formed by the welding of said complementary, terminal turning portions of the pipe sections extends between first and second different points on the longitudinal through-weld of said metallic pipe so as to turn around the axis of said metallic pipe along a peripheral wall of said metallic pipe,   said first and second points being positioned at a distance which satisfies the following relationship: ##EQU8##  wherein a' represents the length of the circumference of the substantially circular cross-section of said metallic pipe and b' represents the distance between said first and second points on the longitudinal through-weld of said metallic pipe.   
     
     
       6. A metallic pipe according to claim 5, wherein said connecting turning weld extends helically around the axis of the metallic pipe.